Poker can generate a wide range of emotions and uncomfortable situations beyond bad beats and unfortunate exits. Here I mention some of the worst feelings that poker players can experience:
When you're not given action with a strong hand: As you mentioned, having a strong hand like KK or AA in the big blind and having all the players fold before you can get value is frustrating and can leave you feeling wasted.
Getting called from weaker
hands and losing: Sometimes it can be frustrating to get called by an opponent with an inferior hand, only to lose the hand on the river. This can make you question your strategy or feel like you're not getting the recognition you deserve for playing well.
Making a costly mistake: Making a bad strategic move or making a mistake that costs you chips or even eliminates you from the tournament can lead to a feeling of anger or regret.
Experiencing a continuous streak of bad luck: Experiencing a prolonged series of losing hands or moments of bad luck can be demoralizing and make you question your ability as a player.